This invention relates to a process for enhancing the purity of a flame retardant product predominant in a tetrabromobisphenol-A.
4,4'-isopropylidenebis(2,6-dibromophenol) is a well known commercial flame retardant and is usually referred to as tetrabromobisphenol-A (hereinafter "TBBPA"). Products comprised predominantly of TBBPA are useful as flame retardants in many macromolecular formulations. The literature is replete with processes for the manufacture of TBBPA, see, for example, U.S. Pat. No. 3,234,289; U.S. Pat. No. 3,363,007; U.S. Pat. No. 3,546,302; U.S. Pat. No. 3,868,423; U.S. Pat. No. 3,929,907; U.S. Pat. No. 4,013,728; U.S. Pat. No. 4,036,894; and U.S. Pat. No. 4,701,568. Two process which produce a TBBPA predominant product having a particularly low organic impurity content are described in U.S. Pat. No. 4,628,124 and U.S. Pat. No. 4,783,556 incorporated herein by reference. While the processes described in the '124 and '556 patents yield products which are useful for most flame retardant applications, there exists a need for a TBBPA predominant product having both a low organic impurity and a low HBr impurity. These low impurity TBBPA predominant products have particular application as flame retardants in polymers and plastics for the electronics industry.